1. Technical Field
The present disclosure generally relates to a grinding unit for sharpening or grinding a rotating knife such as a rotating circular knife. The present disclosure also relates to a cutting machine having such a grinding unit for grinding a circular knife of the cutting machine. The cutting machine is used to cut web material such as tissue wound on tubular winding cores (which is called a “log”) or other “logs” of material such as coreless rolls of tissue. The grinding unit of the cutting machine is capable of grinding the circular knife during the cutting process.
2. Description of the Related Art
In typical applications, a log such as a wound tissue log is cut into rolls of smaller size by a rotating circular knife of a cutting machine. The knife rotates around a shaft, and moves toward the log normal to the axis of the log to cut the log. Usually, the knife is substantially biconical in shape and has an axis and a cutting edge formed at an intersection of two bevel surfaces located at two opposite sides of the knife. The knife has a thickness greater in proximity to the axis thereof and gradually decreasing from the axis toward the cutting edge. Typically, for the purpose of increasing the rigidity and stability of the knife, each side of the knife forms two bevels with different angles. The knife must be ground frequently to restore the cutting edge. Conventionally, two grinding units are provided with different angles corresponding to the two bevels with different angles. Each grinding unit is to grind a corresponding bevel of each side of the knife. Though the cutting edge of the knife is capable of being restored in such a manner, there is a need for a more effective system for grinding the knife.